:root {
  --bg-color: #0d1117;
  --panel-bg: #161b22;
  --border-color: #30363d;
  --text-primary: #c9d1d9;
  --text-secondary: #8b949e;
  --accent-color: #58a6ff;
  --accent-hover: #1f6feb;
  --success-color: #3fb950;
  --error-color: #f85149;
  
  --font-sans: 'Inter', -apple-system, sans-serif;
  --font-mono: 'Fira Code', ui-monospace, SFMono-Regular, monospace;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: var(--font-sans);
  background-color: var(--bg-color);
  color: var(--text-primary);
  height: 100vh;
  overflow: hidden;
}

.code-font { font-family: var(--font-mono); font-size: 14px; }

/* Layout */
.app-container {
  display: flex;
  height: 100vh;
  max-width: 1400px;
  margin: 0 auto;
}

/* Sidebar */
.sidebar {
  width: 250px;
  background-color: var(--panel-bg);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
}

.sidebar-header {
  padding: 1.5rem;
  border-bottom: 1px solid var(--border-color);
}

.back-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.875rem;
  display: inline-block;
  margin-bottom: 0.5rem;
}
.back-link:hover { color: var(--accent-color); }

.sidebar-header h2 {
  font-size: 1.25rem;
  font-weight: 600;
}

.tool-nav {
  padding: 1rem 0;
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.nav-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  text-align: left;
  padding: 0.75rem 1.5rem;
  font-family: inherit;
  font-size: 0.9rem;
  cursor: pointer;
  transition: all 0.2s;
  border-left: 3px solid transparent;
}

.nav-btn:hover {
  background-color: rgba(255, 255, 255, 0.05);
  color: var(--text-primary);
}

.nav-btn.active {
  color: var(--accent-color);
  background-color: rgba(88, 166, 255, 0.1);
  border-left-color: var(--accent-color);
  font-weight: 500;
}

/* Main Content */
.main-content {
  flex-grow: 1;
  padding: 2rem;
  overflow-y: auto;
}

.tool-section {
  display: none;
  height: 100%;
  flex-direction: column;
}

.tool-section.active {
  display: flex;
}

.tool-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
}

.tool-header h1 {
  font-size: 1.5rem;
  font-weight: 600;
}

.tool-actions {
  display: flex;
  gap: 0.5rem;
}

/* Buttons */
button {
  cursor: pointer;
  font-family: inherit;
  font-size: 0.875rem;
  font-weight: 500;
  border-radius: 6px;
  padding: 0.5rem 1rem;
  transition: 0.2s;
}

.primary-btn {
  background-color: #238636;
  color: #fff;
  border: 1px solid rgba(240, 246, 252, 0.1);
}
.primary-btn:hover { background-color: #2ea043; border-color: rgba(240, 246, 252, 0.1); }

.secondary-btn {
  background-color: var(--panel-bg);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}
.secondary-btn:hover { background-color: #30363d; border-color: #8b949e; }

.secondary-btn.danger { color: var(--error-color); }
.secondary-btn.danger:hover { background-color: rgba(248, 81, 73, 0.1); border-color: var(--error-color); }

/* Panes & Inputs */
.split-pane {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  flex-grow: 1;
  min-height: 400px;
}

.single-pane {
  display: flex;
  flex-direction: column;
  height: 150px;
  margin-bottom: 1.5rem;
}

.pane {
  display: flex;
  flex-direction: column;
}

label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  margin-bottom: 0.5rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

textarea {
  flex-grow: 1;
  background-color: var(--panel-bg);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  color: var(--text-primary);
  padding: 1rem;
  resize: none;
  outline: none;
  line-height: 1.5;
  transition: border-color 0.2s;
}

textarea:focus { border-color: var(--accent-color); }
textarea[readonly] { background-color: rgba(0,0,0,0.2); }

.encoded-input { color: #df8e1d; }

.status-badge {
  font-size: 0.75rem;
  padding: 0.1rem 0.5rem;
  border-radius: 12px;
}
.status-badge.valid { background: rgba(63, 185, 80, 0.1); color: var(--success-color); border: 1px solid var(--success-color); }
.status-badge.invalid { background: rgba(248, 81, 73, 0.1); color: var(--error-color); border: 1px solid var(--error-color); }

.error-text {
  color: var(--error-color);
  font-family: var(--font-mono);
  font-size: 0.875rem;
  margin-top: 0.5rem;
  min-height: 20px;
}

.mt-2 { margin-top: 1.5rem; }